Patent Document 1 discloses a water pump including a pump body supported by a cylinder block of an engine and a rotational shaft rotatably supported via a bearing to the pump body. A drive pulley is mounted at one end portion of this rotational shaft and an impeller is pressure-fixed to the other end portion of the rotational shaft.
This water pump is configured such that as a drive force of the engine is transmitted to the drive pulley, the impeller is rotated thereby to effect circulation of cooling water for the engine.